NOTE: If DTCs P1670 or P1671 are also set, diagnose these DTCs first.

Turn ignition on, with engine off. Using scan tool, perform AIR PUMP SPECIAL TEST. If test passes, see DIAGNOSTIC AIDS . If test does not pass, go to next step.
If air pump turned on during test, go to next step. If air pump did not turn on during test, check AIR PUMP fuse (30-amp) located in underhood junction block. If fuse is okay, go to step 4. If fuse is open, check air pump battery feed circuit for short to ground. Repair as necessary and replace fuse.
Check vacuum lines, air hose, in-line check valve and air pipe for leaks or restrictions. Repair as necessary. If no problems are found, go to step 5.
Check for an open in air pump battery feed or ground circuits. Repair as necessary. If circuits are okay, replace air pump.
Disconnect vacuum line to combination valve. Using a hand held vacuum pump, apply 15 in. Hg vacuum to combination valve. If vacuum holds, go to next step. If vacuum does not hold, replace combination valve.
Disconnect air hose at combination valve. Turn ignition on, with engine off. Using scan tool, command air pump on. If air is felt at hose, replace air pump solenoid. If no air is felt at hose, replace air pump.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Diagnostic Procedures